Pulverizing apparatus

ABSTRACT

A pulverizing apparatus in which inner and outer bladed rotors are driven in opposite directions with the blades arranged to produce a flow of air from within the inner rotor to a discharge passage outside the outer rotor and in which the material to be pulverized is introduced within the inner rotor for shearing action by the blades as it is carried toward the discharge passage.

United States Patent 1191 Alpha June 18,1974

I [75] Inventor:

[ PULVERIZING APPARATUS Smith Alpha, Berwick, La.

[73] Assigneef Silver Lining, lnc., Morgan City, La. 22 Filed: Apr. 7, 1972 [21] Appl. No.: 242,154

[52] US. Cl 241/55, 241/52, 241/80, 241/191 [51] Int. Cl. B02c 13/06 [58] Field of Search 241/52, 48, 55, 80, 187, 241/53,188 R, 191

[56] References Cited UNITED STATES PATENTS 335,827 2/1886 Mead 241/52 X 1,816,408 7/1931 State 241 /52- 11/1968 Noe 241/188 R 5/1972 Stephenson et al 241/187 Primary ExaminerRoy Lake Assistant Examiner-E. F. Desmond Attorney, Agent, or Firm-Brumbaugh, Graves, Donohue & Raymond 57 ABSTRACT A pulverizing apparatus in which inner and outer bladed rotors are driven in opposite directions with the blades arranged to produce a flow of air from within the inner rotor to a discharge passage outside the outer rotor and in which the material to be pulverized is introduced within the inner rotor for shearing action by the blades as it is carried toward the discharge passage.

2 Claims, 3 Drawing Figures PAIEmEmummn ammsn ME]. 1 BF 3 PATENTEDJUN I 8 I974 SHEET 2 UF 3 PULVERIZING APPARATUS The invention relates to a new and improved rotary pulverizing apparatus for producing a controlled size product of fine particles from coarser particles.

Rotary pulverizers have been widely used for many years, and although they are effective in their pulverizing action they are ordinarily incapable of achieving anything approaching complete pulverization of the material below the maximum particle size. Thus, where virtually complete pulverization is required the oversized material will have to beseparated from the product and either discarded or further processed.

The pulverizing apparatus of the present invention is I a relatively simple and inexpensive mechanism which for most products is capable of achieving complete pulverization while affording a degree of control over the particle size of the product. It is applicable to a wide variety of products, such as fine marble, clay, barites, oyster shell, corn flour, synthetic resins, limestone, silica, feldspar, talc, cellulose fibers, mica, carbon black and many other products. v

The pulverizing apparatus of the present invention embodies inner and outer bladed rotors driven in opposite directions with the blades arranged to produce a flow of air from within the inner rotor which carries the material to be pulverized through the outer peripheries of the rotors while the blades thereof subject the material to a pulverizing and shearing action. By closely spacing the paths of travel of the blades of the inner and outer rotors and by regulating the relative speeds of rotation of the rotors, effective control of the particle size can be maintained.

Ancillary features of the present invention include, inter alia, a supplementary separator communicating with the discharge of, the pulverizer for effecting further separation of the particles, a baffle system to insure that the pulverizingmaterialdoes not escape the action of the blades within the pulverizing chamber and an array of stationary'blades around the outer rotor to subject the particles to further pulverizing and shearing action before they are discharged from the pulverizing chamber.

For a complete understanding of the invention reference can be made to the detailed description which follows and to the accompanying drawings, in which F IG. 1 is a sectional elevation of the pulverizer of the present invention;

FIG. 2 is a sectional view taken along the line 2-2 of FIG. 1, looking in the direction of the arrows; and- FIG. 3 is a sectional view of the upper duct network of the pulverizing apparatus of the present invention.

The pulverizing apparatus of the invention, as shown I in FIGS. 1 and 2, includes an inner bladed rotor and an outer bladed rotor 11 mounted on separate shafts 12 and 13, respectively, driven in opposite directions.

The shaft 12 rotates in bearings of a pair of upright supports 14, and rotation is imparted to the shaft through a belt driven pulley carried by the shaft. The shaft 13 is similarly mounted for rotation in the bearings of upright supports 16, and rotation is imparted to the shaft through a belt driven pulley 17. The

supports 14 and 16 are mounted on a base frame 18.

tric motors which make it possible to vary the relative speeds of the rotors to control the pulverizing action thereof.

The inner rotor 10 carries a plurality of blades 19 spaced apart in circular array around theaxis of rotation with the blades being oriented to produce an outward flow of air when the inner rotor is driven in the proper direction. The outer rotor 11 also carries a plurality of blades 20 spaced apart in circular array around the axis of rotation with the blades being oriented to produce an outward flow of air when the outer rotor is driven in the direction opposite to the inner rotor 10.

In the particular form in which it is shown in the drawings, the inner rotor 10 includes a disk 21 having a central hub 22 which is fixed on the shaft 12. The blades 19, which are preferably of a rigid material, such as steel, are supported between a pair of annular members 23, and one of the annular members is bolted or otherwise affixed to a face of the disk 21 near the outer periphery of the disk.

The outer rotor 11 includes a disk 24 having a central hub 25 which is fixed on the shaft 13. The blades 20 are also supported between a pair of annular members 26, one of which is bolted or otherwise affixed to a face of the disk 24 near the outer periphery thereof.

The rotors l0 and 11 are accommodated within a generally cylindrical housing 28 which encloses the pulverizing chamber. The inner surface of the housing has mounted thereon a plurality of stationary blades 29, the inner ends of which are closely spaced to the outer ends of the blades 20 of the outer rotor.

The material to be pulverized is introduced into the system through an inlet 30 of a feeder 31 containing a rotary driven screw 32 which discharges the material ata controlled rate into a duct 33. The lower end of the duct 33 communicates with an inlet 34 to the pulverizing chamber withinthe housing. The material is introduced into the region of the pulverizer within the confines of the blades of the inner rotor. Due to the fan action of the inner and outer rotors 10 and 11, the material is carried outwardly and subjected to the pulverizing and shearing action of the blades as it passes between the oppositely moving blades 19 and 20 toward the outer periphery of the outer rotor. The material is also subjected to a pulverizing and shearing action by the rotary blades 20 and the stationary blades 29 as it moves toward the discharge passage 35 in the outer periphery of the housing 28.

The blades 19 and 20 of the inner and outer rotors perform a number of functions; for example, they cooperate to pulverize the material passing through them, to produce an outward flow of air and material to be pulverized, to move the material to be pulverized from within the confines of the blades of the inner rotor to the discharge passage 35 and to confine the oversize particles of the material within the confines of the rotors until they have been reduced to the predetermined maximum size. It has been found that these results can be satisfactorily achieved by orienting the blades 19 and 20 at angles of between 30 and 45 with respect to a radial line passing through the common axis of rotation of the rotors and the respective blade. The

blades of the one rotor are positively inclined with respect to a radial line and the blades of the other rotor and negatively inclined due to the fact that they rotate in opposite directions.

To insure that all of the material to be pulverized will be subjected to the pulverizing and shearing action of the blades, the annular members 23 and 26 of the rotors l and 11, respectively, which are remote from the disk portions of their respective rotors, are located in a common vertical plane and spaced closely together so that only particles of the desired size or smaller can pass between them. Also, material is prevented from passing axially out of the center of the inner rotor by a circular bafile 36 which extends from the inner surface of the side wall of the housing. The spacing between the outer surface of the baffle 36 through which the material enters and the inner edge of the ring member 23 is governed by the same considerations as the spacing between the annular members 23 and 26.

To prevent material from being trapped between the disk portion 24 of the rotor 11 and the adjacent side wall of the housing, a circular baffle ring 37 is mounted to the inner wall of the housing and it encircles the outer periphery of the disk 24. Also, a sealing ring 38 is affixed to the face of the disk 24 near the outer periphery thereof.

Particles which are too heavy to be discharged through the passage 35 will collect in a trap 39 at the bottom of the housing 28. The trap 39 has a removable cover 40 to enable the trap to be cleaned out at the end of the operation.

The discharge passage 35 extends generally tangentially to the direction of rotation of the outer rotor and the housing, and the pulverized material passes upwardly out of the housing 28 and through an upwardly extending separator 41 to a collector 42. The separator 41 is a duct having an enlarged cross-sectional area intermediate the upper and lower ends thereof. The height of the duct and the pressure drop therein will cause the heavier particles to fall back into the pulverizer while the smaller, lighter particles continue on their way into the collector 42. The expanded separator duct 41, therefore, serves as the final determining factor regulating size of the particles.

As shown in FIG. 3, the lower discharge end 43 of the collector 42 is of gradually diminishing cross-sectional area, terminating in a discharge opening 44 through which the pulverized material is discharged into appropriate bins or bags. Some of the air, particularly the air laden with very fine particles, is returned to the pulverizing chamber through the duct 33 into which the material to be pulverized is initially introduced into the system. The inlet end 33a of the duct 33 is located below the closed upper end of the collector 42 and the discharge end of the separator duct 41, thereby preventing particles of pulverized material from flowing directly into the duct 33 and at the same time insuring that the pulverized material is falling under the influence of gravity as it passes the air intake 33a. To relieve excessive pressure that may be built up in the system, a vent 45 is provided at the upper end of the duct 33. The escape of fine particles of the pulverized material through the vent 45 can be prevented by venting the air through a filter medium (not shown), such as a filter bag.

To prevent overheating of the pulverizing chamber, the temperature therein can be regulated and heat dissipated by introducing therein a flow of cooling air supplied by a blower 46.

Summarizing the operation of the pulverizing apparatus of the present invention, the material to be pulverized is introduced by the feeder 31 and through the inlet 34 into the region of the pulverizing chamber within the confines of the blades of the inner rotor 10. The combined fan actions of the inner and outer rotors l0 and 11 product an outward flow of air which carries the material to be pulverized through the blades of the rotors which are driven in opposite directions, thereby pulverizing and shearing the material to a particle size small enough to pass through the rotors. The pulverizing action of the rotors can be controlled by regulating the relative speeds of rotation of the rotors which rotate in opposite directions. Pulverizing material which passes through the rotors will be subjected to a further pulverizing and shearing action by the blades of the outer rotor cooperating with the stationary blades 29 of the housing.

The pulverized material is discharged from the pulverizing chamber into the vertical separator duct 41 in which some further separation takes place. The pulverized material is discharged from the upper end of the separator duct 41 into the collector 42 from which it is discharged into bags or bins and the dust-laden air in the upper region of the collector is returned to the pulverizer by the return duct 33.

The invention has been shown in a single preferred form and by way of example only, and various modifications and variations may be made therein within the spirit of the invention. The invention, therefore, is not intended to be limited to any particular form or embodiment except insofar as such limitations are expressly set forth in the claims.

I claim:

1. A pulverizing apparatus for lightparticles comprising at least a pair of inner and outer rotors, each rotor having a plurality of pulverizing blades arranged in circular array, the blades of the inner rotor being oriented to produce an outward flow of air when the inner rotor is driven in one direction and the blades of the outer rotor being oriented to produce an outward flow of air when the outer rotor is driven in the opposite direction, inlet means for introducing the material to be pulverized into the region within the confines of the inner r0- tor, a discharge passage communicating with the exterior of the outer rotor for discharging in a direction opposite to the force of gravity material pulverized in passing through the outer peripheries of both rotors, an upwardly extending separator communicating with the discharge passage, a collector for the pulverized material, a vent for the upper region of the collector for venting air to atmosphere and a return duct communicating with the vent for recycling particle-laden air to the inlet means.

2. A pulverizing apparatus for light weight particles comprising inner and outer rotors each having a plurality of pulverizing blades arranged in circular array, each inner rotor blade being oriented at an angle of between 30 and 45 with respect to a radial line passing through the axis of rotation of the inner rotor and the inner rotor blade to produce an outward flow of air when the inner rotor is driven in one direction, a radially outward edge of each inner rotor blade being inclined in said one direction, and each outer rotor blade being oriented at an angle of between 30 and 45 with respect to a radial line passing through the axis of rotation of the outer rotor and the outer rotor blade to produce an outward flow of air when the outer rotor is driven in the other direction, a radially outward edge 6 means connecting the upper region of the separator and the collector, the separator permitting the heavier oversize particles to return by gravity for further pulverizing action by the rotors, an air duct connecting the upper region of the collector and the inlet means to recycle dust-laden air through the rotor, and pressure relief means communicating with the upper region of the return duct and the exterior of the pulverizing apparatLlS. 

1. A pulverizing apparatus for light particles comprising at least a pair of inner and outer rotors, each rotor having a plurality of pulverizing blades arranged in circular array, the blades of the inner rotor being oriented to produce an outward flow of air when the inner rotor is driven in one direction and the blades of the outer rotor being oriented to produce an outward flow of air when the outer rotor is driven in the opposite direction, inlet means for introducing the material to be pulverized into the region within the confines of the inner rotor, a discharge passage communicating with the exterior of the outer rotor for discharging in a direction opposite to the force of gravity material pulverized in passing through the outer peripheries of both rotors, an upwardly extending separator communicating with the discharge passage, a collector for the pulverized material, a vent for the upper region of the collector for venting air to atmosphere and a return duct communicating with the vent for recycling particle-laden air to the inlet means.
 2. A pulverizing apparatus for light weight particles comprising inner and outer rotors each having a plurality of pulverizing blades arranged in circular array, each inner rotor blade being oriented at an angle of between 30* and 45* with respect to a radial line passing through the axis of rotation of the inner rotor and the inner rotor blade to produce an outward flow of air when the inner rotor is driven in one direction, a radially outward edge of each inner rotor blade being inclined in said one direction, and each outer rotor blade being oriented at an angle of between 30* and 45* with respect to a radial line passing through the axis of rotation of the outer rotor and the outer rotor blade to produce an outward flow of air when the outer rotor is driven in the other direction, a radially outward edge of each outer rotor blade being inclined in said other direction, inlet means for introducing the material to be pulverized into the region within the confines of the inner rotor, discharge means communicating with the exterior of the outer rotor remote from the bottom thereof for discharging in a direction opposite to the force of gravity material pulverized in passing through the outer peripheries of both rotors, a separator above and communicating with the discharge means and having a greater cross-sectional area than the discharge means, a collector for the pulverized material, passage means connecting the upper region of the separator and the collector, the separator permitting the heavier oversize particles to return by gravity for further pulverizing action by the rotors, an air duct connecting the upper region of the collector and the inlet means to recycle dust-laden air through the rotor, and pressure relief means communicating with the upper region of the return duct and the exterior of the pulverizing apparatus. 